Lead ingestion is considered a major public health problem for infants and children with deleterious effects observed at lower blood lead levels than previously believed. The investigators propose a prospective study of 1000 pregnant women ages 11-30 years, in a triracial community, to examine the role of maternal bone turnover during pregnancy and lactation as a potential source of lead exposure for the fetus and infant (during lactation). The lead sequestered in maternal bone may be mobilized in the process of providing calcium for the fetal and newborn skeleton. This prospective study will allow the investigators to examine lead mobilization from bone turnover in still- growing, adolescent and mature mothers. The specific aims are as follow. 1: To measure maternal blood lead levels and bone (by ultrasound of the os calcis and bone turnover markers) during pregnancy, to correlate these measurements, and to describe them according to characteristics of the mother. 2: To measure maternal blood lead levels and bone (by dual X-ray densitometry, os calcis ultrasound and bone turnover markers) in adolescent and adult women at parturition and at 3, 6, 12 months postpartum to describe the association of these levels by breastfeeding practice and/or maternal growth characteristics. 3: To measure the amount of lead in breast milk and to describe these amount according to maternal bone turnover, growth, chronological and gynecological age, and dietary practices. 4: To measure cord blood lead and whole blood lead in the infant at 6 months postpartum for correlation with maternal lead levels (both blood and breast milk, if applicable), type of infant feeding (breast or bottle feeding), and infant growth characteristics. 5: To relate maternal blood lead levels during pregnancy to maternal blood pressure (during pregnancy), duration of gestation, and infant birthweight. The investigators state that this study has important public health ramifications for understanding if and how accelerated bone turnover in reproduction can accelerate exposure to lead with implications for maternal and infant morbidity.